Generally, a rotation angle detection device (e.g., accelerator pedal device) is provided with a rotation detection sensor which contactlessly detects a rotation angle of a detection object (e.g., accelerator pedal) rotatably supported by a support member. The rotation detection sensor has a permanent magnet for generating a parallel magnetic field, and a magnetism detection member which is fixed in the parallel magnetic field of the permanent magnet to generate output corresponding to magnetic lines of force.
As disclosed in US2002/0175676A1, referring to FIG. 4, an accelerator pedal device has a metal shaft S which supports the rotation of an accelerator pedal 3. A permanent magnet 7 and a magnetism detection member 8 are arranged separately from the shaft S. In this case, the permanent magnet 7 has a substantial fan shape in the rotation direction of the accelerator pedal 3. That is, the permanent magnet 7 is provided with a special shape, so that the manufacture cost of the permanent magnet 7 increases.
As disclosed in DE19503335, referring to FIG. 5, an accelerator pedal device is provide for the accelerator pedal 3 made of a resin. A basal portion 3a of the accelerator pedal 3 is rotatably supported around a bearing J which is made of a resin and has a cylinder shape. In this case, a rotation detection sensor 1 is arranged in the rotation-axis-direction vicinity of the bearing J.
Because the accelerator pedal 3 is depressed by a passenger foot, it is possible for a rough force is exerted thereto. Therefore, in the case where the accelerator pedal 3 made of the resin is supported by the bearing J made of the resin, the strength, the heat resistance and the durability to withstand the operation of the accelerator pedal device are unsatisfactory. Therefore, the wearing away at the resin-made rotation-sliding portion readily occurs during the long term use. Thus, the operation performance of the accelerator pedal 3 will be deteriorated.
As disclosed in U.S. Pat. No. 5,544,000 with reference to FIGS. 6-9, the rotation angle detection device is used as a throttle opening-degree sensor. In this case, the rotation detection sensor 1 is arranged at an end of the shaft S which is rotatably supported. In the case where this rotation angle detection device is suitably used for the accelerator pedal device, the rotation detection sensor 1 is to be arranged in the axial-direction vicinity of the shaft S with reference to FIG. 6.
In this case, when the shaft S is inclined as shown in FIG. 7, the attachment position of the permanent magnet 7 which is mounted to the end of the shaft S through the yoke 2 will vary. That is, the predetermined position of the permanent magnet 7 with respect to the magnetism detection member 8 is deviated. As a result, the magnetic flux applied to the magnetism detection member 8 is varied, thus deteriorating the detection accuracy of the rotation angle.
Moreover, as shown in FIG. 8, in the case where the attachment position of the yoke 2 is deviated in the diametrical direction of the shaft S with respect to the shaft S, the attachment position of the permanent magnet 7 will vary along with the yoke 2. That is, the predetermined position of the permanent magnet 7 with respect to the magnetism detection member 8 is deviated. As a result, the magnetic flux applied to the magnetism detection member 8 is varied, thus deteriorating the detection accuracy of the rotation angle.
Furthermore, as shown in FIG. 9, in the case where the yoke 2 is inclined with respect to the shaft S, the attachment position of the permanent magnet 7 will be deviated along with the yoke 2. That is, the predetermined position of the permanent magnet 7 with respect to the magnetism detection member 8 is deviated. As a result, the magnetic flux applied to the magnetism detection member 8 is varied, thus deteriorating the detection accuracy of the rotation angle.